The nature of temperature history and its effect on the evolution of Ti-6Al-4V microstructure within the laser powder bed fusion process plays a driving role in process safety and component quality. Therefore, the temperature evolution is systematically evaluated and classified according to its influence on the formation and transformation of microstructure. The microstructural formation of the process-specific hierarchical \(\alpha ^{\prime }\) martensite is discussed by reviewing the literature. For the transformation in case of insufficient heat removal, an approach to assess the influence of heat accumulation on microstructure dependent on reached holding temperatures and holding times is presented and experimentally investigated. For this purpose, the Vickers hardness was measured on heat-treated specimens up to a temperature range of 1000  \(^\circ \textrm{C}\) . The observed hardness evolution and its underlying material mechanism were studied utilizing current research findings. The hardness increases significantly between 400 and 500  \(^\circ \textrm{C}\) due to the refinement of \(\alpha ^{\prime }\) martensite. Subsequently, a consistent decline in hardness is observed as the temperature rises from 500 to 850  \(^\circ \textrm{C}\) , attributed to the degeneration of \(\alpha ^{\prime }\) martensite and the precipitation of the \(\beta \) microstructure. Heating above 850  \(^\circ \textrm{C}\) influences the precipitation of \(\beta \) , resulting in an increasing trend of hardness.